I would think you could just use a filter stick with the porosity of frit you need. You could fill the filter stick with either solution (although I would think the solution of your compound would make the most sense) and then put that in your other solution. They make filter sticks with some pretty good sized bores so you should be able to get enough of either solution in there. I would expect it would fit inside a flask without too much trouble, maybe a little cutting. I assume with this effort the standard vial inside of another vial diffusion doesn't work.