Log-Taper Variable Resistor from Linear-Taper
Getting an accurate log-pot to cover 2 decades of resistance (30Hz to 3kHz) is going to be a tall order.

Commercial audio 'log' pots use a 2 or 3 section linear taper because it's 'good enough' for most applications. Even though not 'accurate', one of these would improve the uniformity of turn angle to log frequency over what you have at the moment. I am sure you don't need perfect accuracy per se, but a more uniform sensitivity of turn angle to log frequency response.

A real log pot can be specified, but it would either cost you lots of money, because of its rarity, or you'd need to be lucky and in the right place at the right time to pick up a second hand one.

You may want to consider a 12-way switch instead of a pot. Would 12 steps between 30Hz and 3kHz, which start 30, 45, 70, and finish 1300, 2000, 3000, be sufficiently fine steps? Is the audible difference between a 160Hz and 250Hz frequency setting so big that you need a 200Hz option? Having a switch allows you to pick the resistors to give you exactly the curve you need. I specify 12-way as they are readily available and inexpensive, you can get more ways but the price goes up steeply.

Another possibility is to divide the two decade range into sub-ranges, and switch capacitors. A single switch could switch the capacitor between two values to split the range 30-300 and 300-3k. This would ease the log-law requirement on the pot from two decades to one. You could use more ways for finer sub-ranges, but that's probably not necessary.