After my accident i lost two inches in height, so my just right bike frame is two large. I have seen deda stems are around £21 for a 70/80mm stem. Currently i have my saddle pushed as far foward as i can get it. I have 120mm on currently
If you've lost two inches in height, there may be more going on than necessitates simply the changing of a stem. Two inches in height is a lot.
I'd just start (if I were you) as if setting up a new bike.
1. Set the saddle height: I use the method where I can just lock my knee with my heel on the pedal. It's usually within half a centimetre of my favourite height.
2. Saddle fore & aft: I hold a plumb line from the bottom of my kneeecap with the crank arm level and forward. The line should pass straight through the fulcrum pf the pedal. If it doesn't, I move the seat forward or backward until it does.
3. Handlebar height: this is subject to so much whim and superstition that you can just go for whatever you want to suit your own preferences or adapt to any old injuries.
4. Stem length: Riding on the hoods, I want the handlebar to obscure the hub of the front wheel. If the hub appears ahead of the handlebar, I fit a longer stem. if behind, a shorter one.
All of that can be done with just a length of string with a weight attached (for the plumbline). It takes maybe 20 minutes and will not be too far out. Everybody tunes their own little preferences or adaptations into their riding position, but the method above is a good place to start.
I change the settings in the order I describe because everything is dependent on everything else. I like to get the legs/arse sorted and then move on up.
Good luck and have fun!
