Go to a dollar store and buy a couple of cheap plastic bowls, and then take some scissors and cut an entry into the bowls. This is a cheap and easy way to get two identical hides for a small BP, and they shouldn't take up too much space. Another alternative to plastic bowls is to use small flower pots. These are also cheap, but are a little more difficult to make an entry hole in.

Keep in mind that your 10g tank will probably look a little bit cramped, but it's not like your snake needs to stretch it's legs. A young BP will actually feel more secure in a small environment. If your BP is 27" it may be a good idea to keep your eyes open for a larger tank or tub.

To address your lamp issue, pictures would help a lot! you may have to modify your screen top, or clamp the lamp to a shelf or something above your tank.