I don't know where you are located, but Williams also sells the Fool-Proof receiver sight. It is quite compact and requires 2 holes be drilled and tapped along with some inletting, normally.
: I used to leave the receiver sight block attached to the action, and carry the top-piece in my fanny-pack of emergency equipment. If the scope screws up, it can be removed quickly, and the receiver sight top-piece installed, already sighted in. They're in the $75.00 - $125.00 Cdn, range. With today's strong scopes, I've not had the need of the spare receiver sight . On the .458, I found shooting with a receiver sight to be very accurate, and back in the 70's, it's all the sighting I had for a time. I didn't feel handicapped at all in having it for my only sight. A good Sheard bead front sight completed the arrangement. Flat blade is OK, but I prefer a bead for a hunting front sight.