Have you considered a different type of tank, called a Paludarium?
This is a tank where the top 50% of it is open, and only the lower
50% has water.
Often, mangrove plants or tall emersed aquatic plants are grow to grow up
and above the water.
You can silicone ledges of glass inside the aquarium sides to create platforms
for semi-aquatic critters like newts or frogs or mudskippers, etc.
Just one idea for you, but maybe more difficult in a small tank like 10g.
Another option, to create your divider for soil one side and water the other,
take the measurements and go to the glass cutters and get a small peice of
glass to fit inside the tank, say 6-8 inches tall, that you would then
silicone into the tank at the bottom and sides to create a water tight barrier.
Place this about 50% across the the tank, or so, and in one side put your land and the other your water.
Id recommend a soil type substrate for the land side, so in case your betta jumped out, he would be too abraded by sand, and I would slope it, so he could flop back into the water if he did jump out.
You could plant your moisture, humidity loving plants in that side.
Get a small air stone driven sponge filter for the betta side, and youre
good to go. Just remember you will have to keep the room fairly
stable and warm year round, as bettas prefer temps of at least 74-76 degrees.
Personally, I think this would work best in a 20g setup at least,
but it could be done with careful planning in a 10g.
You could also get a small fully submersible heater for the water side as well.
Never to suffer would never to have been blessed.
Edgar Allan Poe