Please see the first post (and comments) about using an inflatable chair for self-bondage.
I’ve seen lots of posts suggesting using inflatable mattresses wrapped around the body and secured with straps. According to the authors this method works. Also the mattresses are quite cheap.
The suits I found in this shop are not cheap at all. Instead you get comfortable inescapable bondage in a latex cocoon. If you can get into them and zip them up and down without external help, 80% is done.
Now the last 20%. How to safely inflate and deflate the suits in a timely manner.
You can find some suggestions in the above mentioned post. More random thoughts:
- Remove the valve
- Use a remotely controlled electric air pump (for example, connect the pump through an RC outlet)
- Use a timer (e.g. a power outlet with a timer, also see this page)
- The system must not be hermetical to allow the suit to deflate on itself