I still run one on every tank. If you cannot fine one... and you should be able to... then you can make a box out of Acrylic and use a 6100 and a Wave Controller 7092. If you have a huge tank, you can make a larger box with a pair of 6100s in it (or even 6200s or larger). You can use the 6105 as well, but they are more expensive.
There is a used smaller version (up to 150g) on eBay for $125.