ULINE brand of heat sealers come with a extruded plastic strap to keep the handle closed when not in use. Both of mine got lost ... so I made a STL for it.
Might work with cheap EBay China sealers too.
I used a high infill to make it very strong, with 3 outer shells and 3 top/bottom solid layers. I also made mine with ABS. Use PLA at your own risk.