Mark,
Yes, I have enough tyres to be sold separately.
As for inner disks: At a moment I don't have an idea what to offer You. Plan to create a replacement sets for BTR-152 with rubber tyres and resin disks... As an idea: I can try to create resin disks for BRDM series as well or You (and others) want to buy whole sprue
Thanks for the question.
Sincerely, Alexey.
http://www.acemodel.com.ua (Europe)
http://acemodel.tripod.com (America)