Shims can be bought at any motorsports dealer/repair shop. Some will even let you trade sizes. If you're gonna buy one, get one slightly smaller at the same time for when it tightens again.
Bad compression generally means blown pistons rings. It's a cheap part to buy (you'll spend more in gaskets). But it involves complete disassembly of the engine. You'll need a flywheel puller (check your local auto parts for a "harmonic balancer" from their free loaner tools). You'll learn a ton, but even if you're new at it, shouldn't take more than 2 hours till you're cranking.
My friend recommended checking the exhaust clearance. I did so on both the bad ruckus motor and the "good" MET motor
Following measurements of shims using a composite plastic caliper
IN 1.8mm (W/ 180 lasered on it)
The MET motor was in-spec using feeler gauges with the spec being
IN: 0.10 Â± 0.03 mm (0.004 Â± 0.001 in)
EX: 0.19 Â± 0.03 mm (0.007 Â± 0.001 in)
So I'm guessing now means on to blown rings? I really dont want to do this but if this is the only option .. guess I have to