What strap works for you ? - impossible to say, as some like the stiff tight narrow windsurf straps (like me, Dakine Classic are awesome), other hate these and like soft wide straps.
But you should just get some "velcro" straps, any kind will do - then you are sure they will not move and get bigger if thats your problem.
Because it seems that a few of the "super easy adjustable" straps tend to slide bigger, some of them
If the problem "only" is the adjustment range not sufficiently small, you could try using, or if not present, making an "inner" set of holes in the straps, maybe only in one end.
But getting new straps, classic velcro style, will usually solve this issue 100% as they can most often get really small, and will never change size during use