Not sure whether you've got the 180 deg tj07 or the atx one (or if it matters) but koolance do some nice tube res' and brackets to mount on 120mm fan spacings (along the length of the rad) so (for example) you could have a res running lengthways along the midplate (assuming again lol) and screw it through.
Bitspower does that nice stand mount for a tube res and a d5 (see tiny tom logans orca build on yt)
erm.. I think EK have some type of d5 pump tomp/res combo unit that can maybe accomodate a larger tube res? Not sure on mounting though. The EK multi-option res' themselves are pretty good though.