Please don't be offended, but have you looked behind the front bumper for a spare? If there isn't one there perhaps you should consider putting one there. Good luck, Sam
See if there are any bus companies nearby and call them. Maybe you'll luck out and they'll have a used one you can buy. Or maybe the'll direct you to a tire shop.
Try looking for a 315/80/22.5
Now is the fun part of tracking down 6 new tires and saving up to get them and put them on.
Here's some help for you as you search for new shoes for your 4107. This is old info I've posted time and time again, but it's worth repeating:GMC designed the powertrain of your coach around tires that turn 495 revs per mile. This is an important number because:Tires that turn MORE than 495 will lower your fuel mileage somewhat, decrease your top speed, but improve getting started on a slight grade a little.Tires that turn LESS than 495 will have the opposite effect.In addition, you have to consider maximum axle weights - for your 4107 it's 12,000 on the front axle and 20,000 on the rear. Thus you have to look at the maximum weight a tire you're considering will carry - without making your coach ride like buckboard because you've got to have the tires inflated to their maximum.So, regardless of whether you have 22.5 or 24.5 inch rims, keep in mind that the closer the tires are to that magic 495 revs per mile, the closer to the overall performance that was designed into your coach you'll have.Oh, and all HD truck tire dealers will have the revs/mile info in their tire specifications charts.Finally, take the best of your current tires and use it as a spare.FWIW & HTH. . .
Consider Bandag or Michelin recaps for the rear 4. Can save you a significant amount of money. I wouldn't consider any unknown quality companies that recap tires though.http://www.michelintruck.com/tires-and-retreads/retreads/http://www.bandag.com/en-us/index