I would search Facebook Marketplace and Nextdoor - we found a ton that way a few months ago when moving. some people charged and some were free.
We still bought plenty of boxes as well, and have the following suggestions:
1. TV boxes - Uhaul storage stores or HD/Lowe's- expensive but worth the price
2. Large picture/mirror boxes - Uhaul storage stores - for anything nice you don't wan't risk of damage
3. Heavy Duty Large and Extra Large for moving pictures frames, diplomas
3. i think it was the "medium" size boxes, but HD has no handles built in but Lowe's does. not necessary all the time, but was helpful in some instances given the boxes were basically the same size and price.
3. go to spec's or total wine to get free wine/liquor boxes to move your wine, liquor, and anything else glass related since it already has the dividers in the box.
Maybe this was TMI, but having just gone through the ordeal figured i would share.