I got one of the luth-ar a1 sight kits, and it seems those are the only thing I can find available.  I put it together and the aperture is extremely stiff to move, and appears to be drilled off center.  Is there a better option somewhere I'm not seeing?

check the EE here, or GunBroker for GI parts...and forget the commercial junk

It's actually probably due to the flat spring pocket on the modern manufactured A1 type upper, if that's what you're using? They aren't machined correctly to allow the flat spring to compress correctly.

Also, the flat springs are hit and miss on their sizing. If you get an undersize flat spring pocket and an oversize flat spring it can make the fit even worse.

I have a bunch of modern (Brownells) A1 type uppers with the undersize flat spring pocket and I have a bunch of NOS Colt A1 rear sight kits from the The Amherst Depot. All the included flat springs where oversized and would not compress in the out of spec flat spring pockets. I ended up having to buy a bunch of flat springs from RRA which were on the smaller side and they would fit, but they needed to be pre-compressed to actually be able to thread the windage screw through the rear aperture due to the shallow out of spec flat spring pocket... The pocket is out of spec in both length and depth.

It's a pre-brownells nodak upper but I guess they are probably the same?

It's possible, but I'm not sure when these started to be machined incorrectly. All I know is that all my Brownells uppers purchased since 2017/18 were machined incorrectly in that area. And any slick side/A1/C7 type upper that's been made available since has had reports of the same issue with very difficult rear sight installation and overly stiff adjustments.

It's also possible that the location of the windage screw hole in the upper plays a part in all this.

slightly squashing the spring with some pliers can help

I have one of the Luth rear sights that was very hard to move. I took it apart and it had 2 flat springs stuck together.

Same problem, flattening the spring helps.

One of the apertures being off-center is correct per the TDP. That's a built in allowance for the flip up/down movement on the screw

No selling in tech

One of the aperture is supposed to be slightly off center

I just checked the TDP. The L aperture should be offset 0.007" to the right (when viewed from the rear)

Neat, I didn't know that.  It is the L aperture.  I'm somewhat surprised I can notice .007"

I don't think it is binding up on the screw, I will try to smush the spring down and get the tension reduced as you and others have suggested.

Yeah, never had an issue with Nodak or Colt receivers, actually I've never encountered this issue at all. That's probably because I've never used any of the newer stuff like Brownells or LuthAR receivers.