See if you can take a picture. All the part places don't show a pic now that it is discontinued.
Or list the model number so we can look up the schematic.

Just had same issue with part number 664631 at sears. Milling a new one from steel stock for a track drive.

 

I found a couple links for metal replacements vs the OEM plastic, but at $55 - $65 each it probably isn't worth it. Is there any way to glue or bolt the original back together? Maybe get a couple washers / plates and bolt them to both sides as a clamp.

snowblower 631-0002 | eBay

631-0002 MTD Snowblower Track Drive Wheel

Your other choice would be to remove the track system and get a set of wheels for it.

 

Thanks for the help. Yes I know about the wheels change over but my customer likes the tracks because it will drive onto his patio. I also thought of a couple of large disc like washers to bolt it together but I'm pretty sure he would be willing to pay 55 bucks for one. If they are steel he would definitely get them. I'll go take a pic -- be right back.

 

Pics are here
http://s877.photobucket.com/user/yanesnyo/media/snowblower%20stuff/DSCN2054.jpg.html?filters[user]=101974964&filters[recent]=1&filters[publicOnly]=1&sort=1&o=0

 

Working Link:

Snowblower Stuff Photos by yanesnyo | Photobucket