I don’t know of any alternative options for rear sights for the older pistols.
I have read before, maybe here or on GTA or somewhere else I don’t remember, about guys building up the front sight on their pistols by using superglue and baking soda. Modelers use the stuff to build up material and fill in gaps and things. They add layers of superglue and sprinkle baking soda on top and it sets up and hardens up real fast. They can sand it and shape it also. I suppose you could use some kind of epoxy also. The guys I read about who did this to build up the front sights on their air pistols made forms out of plastic gift cards or something like aluminum foil and just added layer by layer to build the sight up to the desired height. The sanded it and painted it to finish it off. Mind you I’ve not done this myself. So I do not know how durable this is but it sounds a little delicate to me.
If your into 3D printing or know someone who is you could maybe try and make a new barrel band front sight. Make the front sight taller and using the trial and error method of file test file test until you get your front sight to the desired height you need. I don’t know anything about 3D printing so have no idea how hard it would be to make a new barrel band for your pistol,
This is about the only option for an optic mount that I’m aware of
https://www.crosman.com/product/crosman-scope-mounts you can also find this on Amazon, probably eBay and other such places. they aren’t super great and are prone to problems like shifting and twisting.
the best option is to go with a steel breech but I’m not certain of the steel breech compatibility with the older model pistols like yours.
I might suggest just leaving your old gun as it is and keeping it for nostalgia purposes and buying a new model 1377 for $60 and installing the steel breech for whatever rear sight or optic you’d prefer. Lots of other options for tricking these pumper pistols out too. So you can go nuts with it if you’d like. That’s what I did. my old rear cocking 1377 that I was given as a kid in the mid 80’s is completely stock. Lots of memories in the pistol. I have the newer 1377 and 1322 pistols and 1300KT pistol and carbine sets ups to play with and trick out however I choose. All of course have the steel breech for what ever sights or optics I might want. I mostly shoot pistols with open sights though.
Whatever you do show it off and post pictures on these threads for everyone
https://www.airgunnation.com/topic/what-have-you-done-with-your-airgun-today/?referrer=1 https://www.airgunnation.com/topic/lets-show-off-our-crosman-pistol-builds/page/14/?view=all#post-1014749 Good luck