written from a guitar players perspective
7#9 is THE funk chord. First among all funk chords.
Many songs go on for minutes with only that chord and variations
Perhaps just tweaking that chord will give you what you want.
If you're looking for ways to embellish consider the common guitar construction of the chord.
strings 5-4-3-2 in key of c notes will be c/e/Bb/Eb on the 3rd fret.
An easy chord to play and a necessary shape in your book.
Slide into the chord from 1/2 (fret) above or below on the and of 4.
Remember the gospel of the 1 in funk. Its the only commandment.
You can also vary the #9 moving to a natural 9 easily in the above form. same timing.
Solid hit on the 1.
A another chord that goes excellent with a vamp like this is built on strings 4-3-2-1
e/Bb/d/G with the e on second fret and the other 3 on fret 3.
This is a chord you will hear all over james browns stuff as the first one above is.
again the slide into the chord from a fret above or below is sweet.
This chord you can also add the high a and or high e both found on the 5th fret strings 1 and 2.
On can argue 6 vs 13th and what not but basically its just another voicing of a dominant 7 chord. Guitars often play chords with incomplete voicings especially those using the upper partials. Its just way the thing is put together.
Point is, play it solid and the funk will come alive in you!
Lastly check out Justin's Guitar Site on the web. He has a ton of funk ideas and lessons.
https://www.youtube.com/watch?v=mF_LazDrYxQIf you don't play guitar I guess this won't help at all.