"...something called silver shiners." You're right; I got it wrong. Silversides.

This, from the care sheet over at Thamnopsis.com.:
Frozen Thawed Fish - this is by far a better option when feeding fish to your snakes. Be sure to use a thiaminase free source. Steer clear of catfish and carp for this reason. Commonly used types include silversides, salmon, trout, and tilapia. Silversides are safe to use and can be purchased frozen from pet stores and sometimes even as people food at grocery stores in the seafood section. They are ideal because they are a whole-bodied food instead of just strips of flesh. If strips of large fish are used it's advisable to supplement with calcium because there is no bone matter.

(hope it is ok to copy/paste an entire paragraph.)

Can your monitor eat anoles, or morning gekos? I'm suggesting them just because, based on care sheets, they seem fairly easy to keep, and possibly prolific enough for a colony to supply an occasional feeder.

I used to raise silk worms for spinning, and while they are seasonal, and you NEED a mulberry tree, they are fun and easy to maintain. They also get fairly big by the end of the caterpillar stage, and very prolific year over year. I ended up feeding the majority to my chickens the last year I kept them, there were just FAR, FAR too many to grow out.