Hmmm, foot pumps. I've used Whale brand foot pumps on boats and they are sooo much better than hand pumps, as (a) you have both hands free and (b) you can get a lot more water through them without excessive effort (and no need to change hands at 100......).
This little one (approriately called the Baby), under 4" diameter works better than most handpumps:
This is the daddy Gusher and it seriously shifts water:
And this oddball Tiptoe may be worth seeing as it is mounted under the floor with just the button sticking out - I can recommend it for a really good stubbed toe:
All of these have two problems:
1) they are boating products, so you need a mortgage to buy them;
2) they work best with the footpedal right at ground level - having to lift you leg up to trailer height is going to make them awful to use.