I have a '96 manufactured home I'm getting ready to sell and most of the outlets and switches are a tan color that doesn't work with the color scheme I'm changing it too, plus they just look dirty. I just pulled the first switch out to find they used a switch that has little plastic feet to hold it to the wall and no electrical box. I'm wondering if there is feet like this that I can buy and use with a standard switch, or if I am going to have to put electrical boxes behind every single outlet and switch to be able to replace them?
I hear where you're coming from; those blue plastic boxes are awfully deep, and are designed to use all the depth of a 2x4, which is not there in a manufactured home because it would make the walls too thick.
Use metal boxes
A standard 4”x4” steel box is 1-1/2” deep and gives 22 cubic inches (room for four /2 cables plus a receptacle or switch).
A deep 4x4 box is 2-1/8” deep. You can put a 1-gang mud ring or plate on either one.
They also make true 1-gang metal handy-boxes, but they are awfully small on cubic inches - they only have room for a receptacle/switch and 1 cable, typically.
If feasible, insert a spacer block so you can screw the spacer to a joist and the box to the spacer.
Metal boxes have a ground screws site intended for a #10-32 screw. They sell adorable little green screws with or without pigtail. Grounds coming into the box must be pigtailed to this. If the box is grounded this way, switches do not need a pigtail and can ground through the mounting screws. Receptacles need a pigtail, though, unless the have a hard-flush, bolt-down connection between their yoke and the metal box, unless they are a "self-grounding" type.
Those switches appear to me made specifically for mobile/manufactured homes and replacements are available from specialist suppliers, eg
Many are described as "self contained wall switches" so that search term may be useful when shopping.
Video showing how to change one, and comments about their safety:
One of the comments suggests you may need a special clamp tool to fit the back on - that may depend on the manufacturer of the switch.