Amazon offers Prime members the World Animals 70-Piece Army Force Bucket for $6.52 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $6.41.) That's $11 off list and the lowest total price we could find. This set includes soldiers, tanks, cannons, flags, roadblocks, earthbags, stones, and a mountain.
Orders placed via 2-day shipping by today, December 22, will arrive in time for Christmas. (This option is free for Prime members but $12.18 for everyone else.)