I have been making feeders for the last few years from plant protectors, the tubular ones, they seem to come in brown or clear, both acceptable colours imo.
I am a part time gardener, so the tubes are free as they have already been used on the small estate I tend, so for them once they have been used, its either me or the tip, so I get in first.
I like a variety of feeders, some with a lot of holes for a faster release of the content,and some with fewer holes, so as they only have a few to start with I just warm up an old tent peg on my blowlamp and melt a few more .
I started by drilling the holes, but the drill was a bit harsh on the plastic, melting seems to leave a small lip around the hole which in fact reinforces it a bit...
I use strips of lead flashing for the weight, it can be varied on the bank by adding another strip if the run if the current is too strong.
They dont look quite as professional as some, but they do the business, the fish dont mind, and I dont worry about losing them as I have squillions stashed away.
David.