I have been in that exact situation too.  In my mind, there is no excuse for a home teacher not fulfilling his responsibility, whether they be Aaronic or Melchizedek priesthood holders.  The issues of a single mother family are enough to warrant additional priesthood service, since there usually is no priesthood holder in the home.  I visit three single mother families that I am assigned to and usually visit at least one more because of a special need.  

  That being said, I would like to add on to what President Siever has said.  If a junior companion cannot motivate his senior companion, he has the same responsibility as the senior companion to serve the families they are assigned.  There is nothing wrong with that junior companion finding another priesthood holder and visiting these families.  

  Whether serving as a senior or junior companion, each home teacher will have to make a full accounting of their stewardship.  Most home teaching assignments take up no more than 3-4 hours per month, about the length of a Monday Night Football game (for those who consider watching Brother Young play football as a worthwhile Family Home Evening).  Naturally, there are exceptions to every rule.  I'm not willing to tell the Lord that I couldn't find that small amount of time each month to visit my families.  

  My experience with slothful home teachers indicates that the home teacher is having other problems honoring his priesthood at home if they are unable to dedicate the time to do what the Lord has asked them to do.  As a priesthood leader, it is my duty to help that priesthood holder as much as he will allow to work through what is wrong with their lives and help them back on the path.  

  For you single sisters who are divorced I would like to ask the question, "Did the problems in your marriage start within a short time after your stopped praying together as a couple and attending the temple regularly?"  I'm not looking to place blame, only to help those who may be heading the same direction.

  On the first visit to a new family, I always give them my business card with my home phone number written on the back. They are always free to call me at home or at work.  (Or by e-mail too).   I want to be the person they call in emergencies.

  On the other side of the coin, I have no problem calling my home teacher if I need help.  Our home teacher was very cooperative when I called asking for help in raking leaves before an Ice storm hit or in rescuing our cat from off our roof.  After helping us shovel dirt back onto our gravel driveway after a rainstorm washed it out, he surprised us one Saturday morning by covering the washed out area with new gravel that he picked up and delivered!  My wife thinks he is the best home teacher ever.

  On occasion a home teacher may need some help working around YOUR busy schedule. I have called my home teachers before and asked them to come over on a specific day, because I knew that if they did not make it on that day, they would probably not be able to connect with us before the month is over. This type of contact falls under the heading of helping the home teachers with their calling.

  There have been times in the past when we have had home teachers who needed some help learning the importance of their calling. To help them get over their reluctance to call and set up appointments, we have called them and set up appointments. Some home teachers need some help from you to make it easier for them to perform their calling.

  A good way to build a bond with a home teacher is to ask for help. Moving boxes, planting a garden, taking zucchini off your hands, helping dispose of an extra lemon pie, etc.

  Yes, it is appropriate to call your Home Teachers and see if they are coming. This may help a "fence sitting" HT get off the fence and perform his duty. It will also let your ht know that you want him to come, are eager for his presence and generally makes it easier for ht.

  I was in the military for a very long time. I had new HT every time I turned around. I found that asking my HT to come visit me, ensured at least a periodic visit. I am now dealing with a priest aged son who doesn't remember Home Teachers coming in his formative years and wants to know why it's so important! Yikes!