Hi WaveRider, surprised to see you wander about here again, heh heh.
Well, the first thing I'd say is to register on PCEngine-FX.com, that's one of the last hangouts for us PC Engine fans besides the Facebook groups and where you'll find some modders and other options.
Second, a guy called chop5 there used to make and sell these ribbon cable adapters that you slip on a PCE HuCard to circumvent the region lock. I dunno if these are still available but it's the cheapest option.
Third, you can find a modder to send your system to mod a US/Japan region switch. Steven Hanley, Shawn, BlueBMW, Keith Kourage are all good guys that can do that.
Finally there is the Turbo Everdrive flash cart, the one that rules them all! This is also my solution as I own one. You load the whole NEC library on a 2GB micro SD card, you got a US/PCE region switch, everything works, you can even patch some PCE games to English and try other fan creations, end of the story!
If you were registered years back on PCEFX, we had group buy efforts to buy Turbo Everdrives on wholesale if you can get 10+ people to join. It's $60 bucks for 10+, so the manager would collect all the money from the buyers, make the order with krik, and after receiving the bulk shipment, he'd ship each out individually. That's how we avoided the $79 retail or other mark ups like at game cave or whatever.
And that's all I got for a thorough answer...
If I procrastinated I might never have responded to ya so I try to reply within days of seeing something if time permits.