I've been trying to address this very issue for a few years.
I'm pretty sure that Pear will indent more than Hornbeam. The 'problem' with both of those woods is the light colour. A dye or stain is OK but if you nick the fretboard when shaping the Neck etc you are left with a problem. Dyes do not penetrate very far into hard woods unless you use pressure dyeing. Pressure cookers aren't big enough and home rigged affairs can be very dangerous. Without pressure you'll be lucky to get it to go much deeper than 0.2 mm's.
Putting a dark coloured trim/edging on the fretboard is one solution. The other is to use Bog Oak or Beech/Oak and cook it in the oven. Both woods are hard enough for fretboard purposes. You can quite easily get it to a Rosewood shade, especially the Oak. The colour goes deep. Oak has large pores but they can be filled, you don't really need to fill them to the usual standard either. I've cooked AB.Walnut (for head plates, not fretboards) and obtained a pretty convincing Black! Wrap the stuff in foil and place a tray of water in the oven.
As ever, test first. Let the wood sit in the workshop before using it. Just make sure it isn't going to crack/warp badly.

Plum wood is very hard, compact and beautiful. Boxwood might be hard to find in a large enough size for the fingerboard but the bridge should be easy. Both of these are harder than pear.

I didn't state that it needed to be Black, dark is good enough. Obviously light coloured woods will quickly show dirt and grime though. Pear is usually a Pinkish/light Brown, I've used it on a Vihuela. I don't think it was the best choice. Laburnum I've also used and that's not a bad option as it oxidises to Rosewood type Brown. Limited widths though and not easily available, same with Plum. You can get these woods but obtaining a regular supply, fairly straight grained, knot free - isn't so easy.

It's an empirical test IIRC, that uses a standard steel ball and either measures the pressure required for a predetermined dent depth, or uses a standard pressure and measures the dent depth. The Janka hardness may not be a good indication of wear resistance, but it's probably the best indication we have.

Is pear a good choice?
Why is always so bloody hard to buy anything in the UK? Any Brits know of a source for suitable pear wood?

Anyone have any other suggestions?

And now you see why it's so hard to build guitars in the UK - it sometimes seems like we have no wood here apart from oak...

That's a good call, thanks.
The wood data base give janka hardness of plum at 6.900N. That's less than pear or hornbeam yet you say it's harder than both.
WHAT'S THE DEAL WITH THIS JANKA HARDNESS?

Well apart from English Walnut, Yew, Sycamore, London plane, pear . . .