I'd go with stud mount breakers of this style.
http://www.waytekwire.com/item/46440...T-BREAKER-40A/
There are lots of options with these breakers, in addition to the one I linked w/o a bracket and auto reset there are manual reset and ones with brackets.
However I posted the one without a bracket so you can use one of these
http://www.waytekwire.com/item/46468...AKER-MOUNTING/ which is available for 2 to 8 breakers, or this 7 bracket box
http://www.waytekwire.com/item/46560...-JUNCTION-BOX/
To distribute the power to multiple breakers you can use one of these buss bars.
http://www.waytekwire.com/item/46568...RCUIT-BREAKER/ again available for different numbers of breakers.
To insulate the breakers w/o using the box they sell these boots
http://www.waytekwire.com/item/23540...AKER-BOOT-RED/
Here is the catalog page with all of these types of breakers.
http://www.nxtbook.com/nxtbooks/wayt.../#/131/OnePage
You should be all in for ~$20 or so depending on how many you actually use. You can also find those style of breakers in a decent auto parts store though they typically will not stock the buss bars, snap in brackets or boots. They also have other styles of breakers such as those used as the FRC main breaker in various amperage and mounting styles.
http://www.waytekwire.com/products/1...cuit-Breakers/