I like my SiTech oval wrist seals. The seals themselves are reasonably priced (unlike DUI Zip Seals) and the replacement process is ridiculously simple. SiTech neck seals are a little more expensive and more involved to replace, but still doable.
Bonus, you can use silicone seals with the replaceables. I just sent my wife's drysuit to DRIS to have her latex seals replaced with SiTech replaceables. They did a great job.
Perhaps the size issue was asked because if you have big hands, the SiTech oval rings can be a tight fit. My hands are just at the limit, especially using the Antares dry gloves that are compatible with the same rings. But I have very large hands... I have only ever met 1 or 2 people with bigger hands than mine.
If you're really worried about fit, or you want a slightly more versatile (but larger) ring system, then SiTech's round ring system might be a better pick than the ovals. Mike at DRIS is extremely knowledgeable, he can probably help you choose the system you'll like the best.
Are you interested in dry gloves as well, or just replaceable seals?