You can make your own sweat box. I have made a couple, one large enough to handle a full pane. You need a pan, a sponge, a mesh shelf to elevate the item in the box and a cover, mine are clear. The largest one was made from the rectangular aluminum baking pan a bent heating vent cover for a shelf and a clear baking pan cover.
Put wet sponges in the bottom of the pan
Put the mesh shelf in above the sponges but not touch them.
Lay the item on the mesh (Gum up).
Put the lid on
If the lid is not clear you can set the pan in the sunlight.
Optionally - You can put the pan on a heating source like a warming tray (NOT a hot plate)...
That will raise the temp and humidity in the box which softens the gum. You should practice on a couple inexpensive pieces first.
It does not take long.
After the gum has softened carefully separate them with tongs then let the stamps/item dry.
Starting out many moons ago, I bought a "Stamp Lift". Same principle but I don't think these are made anymore. Might find one on eBay
though. It is large enough for a block. I still use mine for singles.
I have not used stamp lift fluid but I know Supersafe makes some.