Here's what I'm thinking......
You could make a separate smoke chamber out of your 5 gallon can
Kinda like Al suggested, with a separate intake on your UDS to allow it's connection.
Hopefully others will jump in with some ideas
TJ
I am in agreement with Todd. I thought I had a good idea but then realized when the corny keg is vertical plus plumbing it will be right at about the height of your first grate if it is a traditional UDS build unless the UDS was elevated. Laying it horizontal and using it similar to side fire box really does seem like the best option.