I traded a cowbred broodmare for a foal from her down the line. I get to pick the stud as long as I pay the fees, and I'm struggling to find info on what studs cross well on cowbred.

She's Smart Little Lena/ Bueno Chex bred (https://www.allbreedpedigree.com/weavers+imalena+dee). She's super thick with good bone and hoof, but a little long in the back so probably something with a shorter back. Any suggestions? My budget isn't huge, probably 2k and under.

You need to breed to speed.  I think the biggest bargain out there is Dashin Dynamo. He's in every incentive you can find, and his babies are starting to hit the board. 

I'm going all in on cowbred mares crossed on my Judge Cash stallion.   I'm also crossing my running bred mares on my Metallic Rebel X Smart Little Lena stallion.  

One of the coolest mares I know of is by JLDTH out of a daughter of Peptoboonsmal.

THIS! The new owners of JLDTH are crossing him on cowbred mares. Can't wait to see those babies!

Thanks! I'll have to look into him a little more. John Fame, Cowboys Cartel, and Triple Vodka are some others I've been considering.

You may want to take a look at Famous Bugs - DTF x Bugs Alive in 75 mare. His owners are great to work with! I have a mare bred to him thats due in April. Very excited about the cross!