Hi. Yes it can be very difficult to get good hamster stuff in some countries. It's not that easy in the Uk either! A lot of people rely on custom built cages, but we are lucky there are about 4 or 5 decent sized barred cages available.
If diy is an option, then the cheapest option, if you have an Ikea, is to get two 78cm Samla storage bins, cut one end off each of them so you can join them together, and then hot glue them together to make one longer bin
Otherwise, maybe the biggest plastic storage bin you can get. It would also need a panel cutting at the front at least, and mesh putting there for ventilation. Also a lid could be tricky - you'd probably have to cut the ends of both lids and hot glue them as well and then cut the panels out of the lids and mesh them.
Bin cages can be a cheap option, but the downside is needing a few tools to make it. I'm not sure how hot glueing works. Meshing them is not too difficult - you'd need to punch holes and use cable ties and possibly some masking tape on the outside. Cutting the plastic panels to mesh them can be tricky to ensure they don't crack - I think even heating a pen knife might work - if done safely! Or asking someone who has a hot knife.
Bigger tanks can be hard to get hold of and can be very expensive in some countries. You could look out for a second hand fish tank - they may be pretty grimy and need cleaning up inside first. Something 3feet or 4 feet long is good, providing it is deep enough and tall enough. So it would need to be at least 18" deep and 18" tall. Ideally 20" deep and 20" tall. Something like a 40 gallon breeder tank, if a 75 gallon tank isn't available.
Other than that it's making a diy cage. Again a lot of people rely on Ikea hacks.
The wheel rainbow linked would be fine but it might fill the tank.
It's really great that your hamster is out a lot with you at night
Giving out of cage time will really help if he's in a small tank. It's perfectly normal for them to sleep all day though
They are awake all night and asleep all day usually and often don't get up until midnight. You could get him in the habit of waking a bit earlier maybe, by putting food out around 7pm possibly, and making a little bit of noise in the cage while doing it. They can get in the habit of waking up at feeding time - especially if they can smell fresh raw veg!
As well as his hamster mix, a tiny bit of fresh veg each day (every 3 days for the first two weeks, then every day) is good for them. There's a safe veg list on the home page on here
I am looking forward to hearing more about your hammy and if there's anything we can help with, sourcing things, we will help