There are different methods for circuit breaker tripping. Thermal, it gets warm or hot, then trips. Magnetic, the field strength get to strong, then it trips. Magnetic are more reliable, and not effected by outside temperature, but cost more. Thermal breakers are cheaper, but less reliable. Most circuit breakers in power strips are thermal breakers. Whatever type you use, I'd suggest having a couple spares of each size you use unless it is commonly available in which case keeping around a spare for each size should do.
Panel mount breakers are what is standardly used on boats. BlueSea is a manufacturer that caters to the boating market. Prices are high, but many boating supply places handle their equipment. Maybe enough coverage to not worry about having spares.
I picked up my last set of breakers from DigiKey. https://www.digikey.com/products/circuit-protection/en
They are an electronics parts supplier. Prices are good, they have a minimum order size, but they have everything.
TE Connectivity Series W57 https://www.digikey.com/products/en?FV=ffec07ea&stock=1
and W54 https://www.digikey.com/products/en?FV=ffec0dc4&stock=1
looks close to what you were showing. Other makers produce similar parts. They will mount into a simple hole drilled into a panel. Check the termination of the type you choose because they can vary. I prefer to use 1/4" quick connects which most of these are. Carling Technologies https://www.digikey.com/products/en?FV=ffec07e6&stock=1
has ones that can do both 250VAC and 32VDC.
I typically get TE Connectivity Series W28 https://www.digikey.com/products/en?FV=ffec00d5&stock=1
They are an inexpensive but reliable thermal breaker for up to 250VAC or 32VDC, and you can drill a slightly oversize 5/8" hole in a 0.03" to 0.06" thick panel, and mount them by just snapping into the panel. They also have 1/4" quick connects so wiring them up is easy. They will need a 2.5" or deeper box. Other types of breakers can go into shallower boxes.
Waytek Wire is a place that specializes in the DC wiring needs for vehicles and trailers. Their circuit protection page https://www.waytekwire.com/products/136 ... rotection/
Their price for bulk crimp on quick connect terminals is great. You could spend more getting two packs of 5 from your local auto store than 100 from Waytek. They also have spools of wire, tail lights, trailer pigtails, etc.
Yeah, a standard electrical junction box could be used for holding the breakers. Follow maximum wire loading requirements for box loading, and don't mix AC and DC wiring in the same box. I'd look at using some of the exterior boxes that have a more finished look to them. As a note, when making a wiring panel with circuit breakers, I try to keep input and output wiring separated.