My little two cylinder steam engine model will need to have the cylinder lapped. I found these thru-hole-laps on eBay. Found some diamond grinding compound on the bay also. The lap 15/16 diameter was close enough to the 1" spec'd size for the piston and cylinder that I could not pass it up for about $6.00 with shipping included! However it was just the brass lap...Needed the support shaft and the tapered plug for expansion. Easy enough to turn and thread a 1/2-20 piece of steel for the shaft and then taper a piece of 1/2-20 all thread for the plug. Should work great and save me the time and brass for making the lap.
Here is a great video by Suburban tool on through hole lapping:
Don has a lot of excellent machining videos on the tube.