well I made myself a stir plate from crap I had in my garage didn't have to spend a cent then I need a stir bar and the prices for those things are crazy unless you buy a bag of them. so I made my own. here's what I did.
I used a piece of an old plastic racking cane I had from my first brew kit. cut a 1" piece off and cut a screw that fit tight inside to just under 1".
I then put the screw inside the plastic tube.
the I cut a small piece off the racking cane to melt into the end of the stir bar.
I let the plastic burn for just a few seconds to let it melt into the stir bar and push it in with a screw driver. be careful not to let it burn to long or the plastic will turn brown.
then I carefully grind off the extra plastic.
then I use a file and by hand file it into an egg shape so the ends are narrower than the middle. I made one without doing this but it did not spin well.
I then insert the bar into the end of my drill adapter tape it in and center it as much as possible.
with it in the drill I carefully grind it against a file to round it as perfect as I can into the egg shape and then sand it with 400 sand paper and finally wet sand all while the bar is in the drill.
here's the finished stir bar. made two because the first one I cracked while making it because I put it directly in my drill and tightened it to much. took me about 20 minutes to make the second one and now my total cost for my stir plate is still $0.
here it is spinning up a nice vortex inside a 1L jar I had on top of my DIY stir plate.