An 18 mm Tropic strap would fit the bill. They are available used, NOS and re-popped. A simple ebay search brings up quite a few.
If you would like a beads-of-rice bracelet, the best way is to buy a "humble" Enicar with one fitted. Usually much cheaper than buying the bracelet alone...
The pointer ring for the 36 mm watches used to be somewhat available but supplies seem to have dried up lately. Hopefully someone will have a spare they are willing to sell.
I have found the Guide 33s to have a more varied spec than the "regular" Guides. Don't be too quick to think they need parts replaced to make them "original".
Should you keep it? Of fricken course! Lovely watches. Beautiful on the wrist though perhaps dangerously distracting at times. My watchmaker had a stunned look on his face after overhauling my 126/001. Even better, yours is a bit worn so you can wear and enjoy it with no feeling of dread...
Here's one in near NOS condition that is similar to yours:
https://www.chrono24.ca/enicar/sherpa-guide-33-mk2-ref126001-7-63-world-time--id26282662.htm
Love those Imp engines!
I have a ‘68 Lotus Europa S1 and a ‘69 Lotus Seven S3 myself but no matching watch straps. I do have a Heuer Rally Master in the Europa though.
The red pointer ring shows up on ebay. There is an orange one up right now and a red one sold just last week. The retaining spring can be made up from suitable piano wire.
There are no new parts, all are NOS. This means that plans of making it water proof again are a bad idea. Fix it up for careful, casual use. So, only change what you have to change. If the crown looks fine, reuse it. Same with the stem. Crystals can be polished and will look excellent...