Rear sprocket spacer

I need a little more clearance for my chain to clear my new Avon 150/80-16. Before everyone jumps in and says that its too big for a 3" rim, Avon lists appropriate wheel size as 3-4.5, and Harleys have been running 150s on 16x3 wheels since 04 or so.

I found GPZ 750 sprocket for the front. Fits like stock but has an adittional 5mm offset. The rear is giving me problems. The only sprocket spacer I can find is 9/16. I'm thinking of having tho old sprocket turned down to make a spacer, but I thought I would check here first to see if I'm overlooking a readily available source.

Perhaps a machine shop has a 5mm spacer that they could adapt to fit your sprocket carrier.
I would guess they have round blanks. size estimate would be 80mm ID x 120mm OD x 5mm thick. ???

I think to machine a spacer from scratch would cost more than just shaving down an old sprocket. They would have to machine the ID, the OD, and drill out the bolt pattern. If I have a sprocket shaved that is only one operation. I can cut off outside with quick cuts between the lightening holes and use a file to match the OD of the hub myself.

Just wanted to make sure there wasn't something I could just buy without having to deal with finding a machine shop.

I have used old rear sprockets as spacers. Cut everything around the mounting holes off, chuck it up in my lathe, true it all up then tack weld it to the original sprocket.

Simple enough. But while I love excuses to buy tools, a lathe is more than I can justify.

An older guy from work that runs vintage Bultacos promised to show me ways to get creative with a brake lathe. Hopefully that'll do the trick.