UPDATE: I no longer use these. They worked, but I highly suggest making the Dennis Brown BED hold down clamps outlined in his Facebook post, it will make your autoleveling much more consistent.
As far as holding the glass down what I now do is this:
1) pull that stock build surface sticker off like a bad bandaid
2) apply a couple squirts of hairspray onto the bottom of the glass plate. Carefully place the glass plate on the aluminum heated bed so that it is well centered.
3) allow 20 minutes to dry.
The glass plate is now very well held down without any additional clamps.
These will hold a 120mm glass plate on the bed of your monoprice mini delta quite securely. You also get some nifty shields that prevent debris from falling into the bottom of your printer. This is a remix of 2 good designs on Thingiverse and I think they are better combined than separate. The reason is that this design doesn't allow the clips to spin, which with previous glass clips on Thingiverse could allow the bed to get free mid-print. These are designed to hug the stock clips tightly, so they become a second point of contact and add to rigidity. You'll want to clip the shield end of this part higher up on the rails, and then slide it down, you'll probably have to wiggle it back and forth a bit to get it over the stock clips.
DEFINITELY CHECK: Each time you re-install your glass plate, make SURE you can still hear the tact switches under the bed click if you press your fingers on the three spots where it goes to auto-level. I'm not responsible for any damages caused by the use of this print.