Random notes:
+ The Williams and other traditional US sights use a 7/32 x 40 eyepiece thread; both German sights use a 9.5mm X 1.0mm thread. Each is a standard size shared with other brands. Many accessories are around for both, which opens up future upgrades.
+ "Plus One" on the Tech Sight, a very nice, very compact, and rock solid design. Note that it has a proprietary way of doing different opening sizes - does not use standard screw-in eye disks. If you buy one, go for the optional aperture kit, and adjuster tool. As Mycapt65 mentioned, a significant advantage is that it can be mounted further to the rear than a Williams, which must go forward of the side-button safety. Link:
https://www.tech-sights.com/product/remington-597-adjustable-aperture-sights/ + I agree on that Daisy sight. Heavy, slack adjustments, poor small sharp attachment "foot," and made for a flat rail, not the 35's arched receiver top. It's one of the few sights I've ever sold! Beware the same basic unit is sold under other brand names, too...run away.
+ The old HW and Anschutz sights are relatively plentiful, but alas - no longer made. It takes a little patience and scouting around to find one - auction and classified sites, gun shows, etc. The HW sight was made with two different rail spacings (went from 13mm to 11mm around 1980); verify you're getting an 11mm one for a new 35.