I wouldn't shy away from less-than-custom flintlocks. It's just that if you are going to rely on a flintlock then you might want to go all out. By rely, I mean sell your other guns 'cuz you're going to make do with a flintlock.
But if you plan on keeping your cappers then T/C and Lyman is just fine. That way if you aren't confident with your flinter in all conditions - you can fall back on a caplock.
Don't necessarily assume you can't afford a semi-custom either. Remember you have some money in the guns you already have. I already had a GPR caplock in .54. I could spend another $300 for a GPR in flintlock, same caliber. I knew one gun wouldn't get used.
Instead I risked $850 on a semi-custom flintlock, carefully researching how to get reliability. Then after I was satisfied with it's performance, I sold the GPR for $215. So that was a total of $635 for the flintlock, and I use every penny's worth of it.
There's ways of saving the money and spreading the cost out. You can buy the barrel one year, the lock the next year. Then send the barrel and lock to a gun maker to "stock" it. He then returns it to you for final finishing. You saved yourself %11 from the Pittman-Robertson act, and in any given year you didn't spend a whole bundle.