Well, my very first thought is the Gardens of Morr set from ol' GW itself.
That gets you, for $50 (well, or less since I'll assume even your FLGS beats GW website prices), three tombs, plus a gate, plus a statue, plus some walls.
I'll admit, for generic tombstones I tend to just say 'cut them out of plasticard/foam' as that is cheap and will give you a lot.
I suppose if you want fancier stuff there's Reaper's stuff.
Some may not fit your look, but I'd note that for less than $3 you can get the P03122D sprue with 3 different types of tombstones that all look pretty darn good. Snag that up a couple of times, maybe one or two of the fancier ones, and a handful of DIY ones from foam and you should be able to have a pretty extensive pile of headstones for a pretty minor investment.
I'm pretty sure I've seen some of the cut wood guys selling tombs as well depending on your opinion on laser cut stuff. I'll admit none of the ones I have bookmarked have anything perfect for you, but I would wager it's out there.