I am sure there is a small bulb there but knowing Subaru, you will have to buy the whole switch.
I once wanted to replace a small bulb on another switch only to find out that one has to buy the whole assembly....
On LL Bean, and others, be careful of breaking the "bezel"
For me, the worst part of replacing seat heater switch bulbs was pulling out the "wood" bezel that frames around the shifter and 1/2 way up the dash. If I remember right, pull up on the back (toward the back of the car) part of the bezel until it pops out and no more - you may need a putty knife for this.
Don't pull up too high on the back part because the next step is to pull straight back on the vertical part of the bezel to release the "pins" on the bezel. If you pull up too high on the rear part of bezel, you may break the plastic pins on the front.