If you do a search of this site, you will find that this topic has been discussed at length.
In a nutshell:
A number of suppliers just threw in the towel. Too much hassle and I can't blame them.
Several suppliers are thinking about strategies for getting these engines epa compliant, like Mike Montieth and George at Utterpower.com.
A number of us anarchists realized there was no prohibition on importing parts.
You know, like a crancase, a crank, a cylinder, a head, piston assbly, etc. and discreetly thumb our noses at the nice folks at the epa. This would actually simplify the process for most of us, since the engines almost universally require disassembly for cleaning and removing of retained sand, improper assembly, etc. This might save us a set of bearings and rings which often get chewed up by the demo run done over in India.
And of course, Hotater's Idea, along with Mr. Lister, is to buy a bunch of original English Listers, which are not prohibited in any way, and ship a container load of them over here, overhaul/freshen and again discreetly thumb our noses at the beaurocrats.
If I recall, part of the nastiness is that if you overhaul a stationary engine, even an old english one, you could lose your grandfathered status and be required to bring things up to spec, tier I, or tier II, or whatever is in force at the time.
Don't the beaurocrats have anything more useful to do???
So we're not out of the game, but it is definitely a whole new ballgame.
Good luck and have fun!
troy