Just recently discovered an excellent eBay source for 2700 series Lehman parts.
Doug is very easy to work with, timely communication, and really good prices. I accidentally ordered rings for a Dover engine, and seeing that I ordered a Dorset piston and gasket sets, he emailed me to make sure I wanted those rings. Good catch! He had no problem fixing the order, and refunded the price difference for Dorset rings.
No affiliation at all, I just highly recommend him.