I've seen Lyman 48s on Brit and German magazine rifles but I've always assumed they were installed after the rifles arrived in the US or perhaps were special ordered as such. Another option would be the Lyman 36 which mounts on the bolt release, hard to find and $$$. You don't see those on Brit rifles much, though. The Lyman model which mounts on the rear of the bolt striker (can't remember the model # and too lazy to look it up) was used by several Brit makers. I think I remember seeing it as an option in Jeffery's catalog. Recknagel makes and sells a Rigby type bolt peep which is pretty neat. I've never seen one of their's but the Rigby system is neat. I've never seen a Holland sight for sale and when I asked them about 15 years ago they said they were no longer making it, either. That's a fairly neat sight, too.
So, short answer, search for a Lyman or order a Recknagel. HTH