The cemetary my mother and grand mother are buried in won't let you plant anything. My mother was an avid gardener and president or officer in garden clubs and I was going to plant a low growing (4" tall at maturity) blooming ground cover. They pitched a fit. You'd have thought I was going to erect an out house on top of the grave of one of their beloved politicians!!!
If I was going to brave their wrath (and the law) I would plant crocus. It blooms early in the spring, grows very short and will spread. If you want something that is a "grass" and will be somewhat pretty, plant clover. It has shamrock type leaves and pale green/off white flowers and will self seed.
As far as getting the bulbs goes, the cemetary I mentioned above clears the graves every Wednesday and puts all the stuff in a low sided dumpster that is about 4' tall and about 20' long. I've seen people take plants and pots out of there, in front of the cemetary staff, and no body seems to care. If nothing else, throw the greenry away and use the potting medium around your garden. It keeps it out of the landfills.