I found an interesting version which goes up to 2.5 megahertz. In their datasheet it talks about exactly that, being able to run a stable mode with one resistor.
http://www.aldinc.com/pdf/ALD7555-7556.pdf
That part is not cheap, but it does have impressive PSRR on the graphs. (tho not reflected in the tables ? )
And for a bit of a twist in 555 variants, here's one built with a (non-volatile) programable decade counter:
https://www.customsiliconsolutions.com/downloads/Revised%20Standard%20products/CSS555_Spec_2.pdf
(see page 2 for a block diagram)
Coming from a 12C509 programming history, after all these years I'm still not exactly sure which niche the CSS555 fulfils.
Yes, the CSS555 is also not cheap. However, it does manage good precision with small caps and low uA. (typ 1% and 35 ppm/°C )
MCU's alone struggle to match the Icc/precision levels, as most low power oscillators in MCU focus on power first, and dF/dT and dF/dV later.
Many fail to even spec tempco and PSRR of their low power osc.
The emergence of 20c MCUs has pushed the low power 555 into smaller niches.
A MCU with a 32kHz crystal can still cost less than a CSS555, and the crystal leapfrogs into much better precision.
Some MCUs allow you to calibrate the poor kHz osc against the better MHz osc, at some small code and icc cost.