Not sure what your needs are, but many people interested in audio (myself included) use vintage analog audio millivoltmeters for audio-frequency AC measurements. With the burden of bandwidth off your chest, you have many considerably cheaper but reasonably high quality DMMs to choose from.
An interesting option you might want to consider is a vintage HP400E (or EL - both capable of dBm readout) coupled with a cheap (or not so cheap) DMM of your choice. Not only these HPs have an impressive bandwidth, unmatched by any DMM (10 Hz to 10 MHz), but they also sport a DC output (scaled to 0-1 V for any input range). They can act as wide band amplifiers and AC to DC converters. You can connect any DMM to the DC output and get a highly accurate digital reading, if you wish.
I paid $14 plus shipping on mine on eBay, a couple of years ago. With a little patience, you can get one under $50 shipped.
In the example below, I fed a (challenging) signal of 1 mVrms, 100 KHz (from my Siglent AWG) to a HP400E (which displays it correctly as 1 mV on its analog scale), a BM689S (which cannot even measure it) and a Fluke 189 (which measures 0.919 mV) – both in AC mV mode. The meter on the right is a Fluke 87V in DC mode (impersonating here a cheap DC voltmeter connected to the DC output of HP), which measures 0.9971 mV (factoring in the scaling). The same signal measured with my DMM6500 is 0.9986 mV, which is probably the most accurate value I can get by measuring directly the AC signal. Note that the digital reading of the DC output of the HP400E is the closest to that. I could measure with no issues a signal of 3 MHz as well, just for the sake of it.
I have a HP400E, which has a linear mV scale on top and a logarithmic dB scale underneath. There is a HP400EL version as well, with a linear dB scale on top and a logarithmic mV scale underneath (if scaling directly the dB to 0-1V is more important to you).
Just a thought.