Assuming Uncle Seiko has the end links you need, his bracelet is compatible with the appropriate Omega clasp cover:
https://www.ebay.com/itm/264852869324
The clasp cover is held on using special spring bars, so it is easy to change.
The Forstner uses an incompatible clasp type, so you can't change just the clasp cover; you have to change the entire clasp. It can be done, as I have done it, but that takes somewhat more experience, or your watchmaker can do it for you.
The Forstner is arguably the somewhat better bracelet, but it is more difficult to adjust the size, you have to change the entire clasp, and it's more expensive. The Uncle Seiko is easier to adjust, you only need to buy the clasp cover, and it costs less.
Either is a good choice, it just comes down to what you want to do. Forstner's 19mm ends are specifically designed for the FOIS, which is not necessarily the same size as other 19mm-lugged Speedmasters, so there's that.
This clasp should fit the Forstner, as I stole mine from an 1171 bracelet:
https://www.ebay.com/itm/294187534801
Good luck!