I have a 1970s Bob Jackson frame that's got clearance for fenders, but no eyelets. It needs repaint badly, and it had occurred to me to have eyelets brazed on when doing that -- however, something about this troubles me: I'd prefer to leave the frame in current state, which is pretty devoid of braze-ons.

Don't even bother mentioning P-clips, I'm ag'in' it! In thinking about this, it seems entirely possible to make a plate fixture with hole for mounting fender stays, and a larger hole for the axle. It's true that I'd have to remove the QR skewer to remove the wheel, unless I can think of a way to slot it, and key it to the dropout slot. A slightly different approach would be to braze a tab onto the part of the stay that wants the eyelet, with a slotted hole for fitting between dropout and skewer surfaces.

Anybody ever seen a commercial product like this (other than a P-clip!)?