Bretonnians by GW would be great! I personally have bought a couple of boxes of Northstar Military Figures' Fristgrave Knights, which is a good price for ten plastic knights per box with a more adventurer aesthetic and tons of weapon and customization options.
Perry Miniatures also sells boxes of both foot and mounted knights, with the Agincourt knights being very flexible and extremely affordable.
Lastly, the original rules were written and playtested with 2" tall knight toys bought in a $10 tub!