Many players struggle along to varying degrees with an instrument that does not fit their hands well. The instrument may actually feel “normal” but there is a new normal that could open up more technique and comfort with some minor adjustments. One of those adjustments is extending the levers to meet the fingers better.
Ideally the fingers will at a very natural curl hit the valves perfectly. This is often not the case, especially some older brands and models of horn made in a period when horn playing was more male dominated. But even very recent horns can benefit. My main, go-to horn for over ten years was a Paxman 25A which I modified with these purpose-made “dimes,” made for me by natural horn maker Richard Seraphinoff. I like these better than real dimes, which are often used, but are a little large in diameter. If you do use real coins, I always suggest to students to go to a coin store and shop for at least a set of Liberty silver dimes, they are a bit smaller in diameter than modern dimes and wear better as they are solid silver. But besides that there are other alternate small coins from other countries that may strike your fancy. Larger coins are bad as they will tend to pinch your fingers between the levers.
Any repair shop with a lathe and brass rod stock can easily make up a set of these just like mine at a low cost. One maker that sells these for example is Stuart de Haro, who calls them in this page in his site (scroll down to the bottom) “Finger Cups.” His are available in brass or nickel silver.
Wherever you obtain them, they are a very simple matter for a qualified brass repairman to solder on to the instrument (don’t use super glue!) and can make a huge difference for hand comfort.