Omega deployant clasp, will "regular" straps fit?

While the clasp might fit, it likely will not fit your wrist very well - the length of the strap for the pin buckle is considerably shorter than that for a loopless strap. This will cause the center of the deployant to be off center, and probably close to the edge of your wrist. The non-buckle strap will also likely be too short and might not allow it to fit your wrist.

If you don’t want to pay the price for an Omega deployant strap, there are lots of aftermarket options that will fit the deployant clasp, in leather and rubber. Some as cheap as $50.

You can attach the clasp to the strap, but...

1. Deployant straps are usually different lengths. For example, a standard 110/70mm strap fits my wrist perfectly, but for deployants a 90/80mm fits me.
2. The notch for the buckle tang will be visible.