I have noticed a few new searches getting here looking for microloading ideas. I have had great success in using big steel washers.
Go to McMaster and search for part number: 91081A046
McMaster has great service and ships FAST!
These work great for microloading olympic sleeved equipment, grip machines with an olympic sleeve etc. The washers weigh about 5/8lb each. 8 to a pack.
Specs:
91081A046
Plain Steel USS Flat Washer 2" Sz, 2-1/8" Id, 4-1/2" Od,.153"-.213" Thk, Approx 8/Pk
In stock at $11.37 per Pack
This product is sold in Packs of 5 Lb.
Also, do not forget about PlateMate Magnets. Some scoff at the $25.00 price per pair, but they will last a lifetime and are INVALUABLE for Blob/Pinch training. They got me to "The Blob".