Can I install a pick guard on my bass which doesn't have a pick guard?

That model was never offered with a pickguard, so unfortunately, there's no OEM replacement to buy. And I doubt there's an online supplier who has an existing template for that particular instrument – but as the expression goes: "Never say never."

Your best bet would be to get a price quote from one of the many custom pickguard builders out there. You'd need to supply them with a specific design to follow, either via a very precise tracing or a digital CAD file, and then specify the material you want. If you're concerned about how many screw holes to use and where they should be placed, the vendor may be able to assist, or perhaps ask a local luthier for his/her advice.

 

Please don't cover the beautiful Exotic Wood of a TRBX174EW:

The machine-heads are the weak point on those IIRC. I had one for a bit & the machine-heads liked to slip when tuning up.

 

You have to design your own pickguard and have it custom made. If you use double-sided carpet tape rather than screws to hold it in place you can take it back off to show wood without damaging screw holes showing. I did this to my G&L L2500s that never had pickguards. They can be played with or without pickguards and I can switch the pickguard colors around to suit my mood. For example I also have a Tort guard that often is put on the natural Tribute. Looks great!