The Peltiers...
There are few cheaper ones at Jaycar around $20, all 40x40mm. The
smallest one may be able to run at our power levels.
Then we move a step up to RS/E14 and similar shops and the prices start at $40. Large range of Peltiers to chose from, even stacked ones for over $100.
After lots of reading it looks like running the Peltier at about 70% of max power is the best for long life. This means that we should look for about 15V Peltier that runs at less than 4A.
For example, something like
this at 12V will give us around 3A max current. The max temperature differential will be about 40deg.
Or there is a fancy dual-stage Peltier
here. A bit pricey at $100 but it should be able to achieve temperature differential of 95C!!! However, the cooling power is 8W only... I suppose that will be the main question, how much cooling power do we really need.