there are good ideas here if your into bondage/restraint or rope play and it wont have that cost your trying to avoid.
https://www.selfbound.net/sbtechniques.html
I've used a lot of them with onliners over the years. Most are FemSub orientated but I use them with Malesubs too so they will work for you. The safety and positioning is often interchangeable. Several body harness are also easy enough to do on yourself . There are also several handcuff ties about online and hogties (if you can find any give me a message and I'll send you some. In fact anytyhing here I can help you with)
You might also like to explore CBT and preform that on cam for your Master too. Several techniques you can use "pervertables" that you can find in dollarstores. Some easy toys to make are a butterfly board or press (I personally love the plexi ones) if the CBT does take your fancy.
You can find many examples of these online, they are pretty easy to make with minimal ( power)tools.
A good collection of pegs(clothespins) clips and clamps are pretty cheap and easy to find in general stores. If you haven't made one already a peg zipper can be fun!
Chopsticks or drumsticks and few rubber bands can be easily turned into a humbler and self applied. the rubber bands can also be used to flick too. If the pegs above are to bitey, a rubber band onthe top can adjust the clamping power.
Another idea might be a rope flogger, they are easy to do and cheap.
Spreader bars are the same..easy and cheap, a broom handle and screw in "O" rings will do the job in a pinch.
Another idea for a longer task might be for your Master to write a story you can either film or photograph. You could then re enact a scene a night (or as fit)
suction cup anal toys can also be a bonus as it can free up your hands. If not try wedge a dildo/Dong between mattress or even a set of bedroom drawers will work...but the suction cup toys are way easier
You could also look into Domination by Proxy and pay for a Male ProDom and have your Master there on cam. (just make sure you ask if the ProDom is ok with this)
If you do want to spend money...look into toys that are wifi controlled.
I just noticed this member appears to have moved on...but heh! I'll post anyway (might help someone else that is stuck for ideas)