Reduce the frequency of a saw resonator

I have a cheap chinese transmitter which sends RF at 422.92 (I suppose) MHz.
I need to send bits at 433.42 MHz.

Can I somehow hack the module to change the resonator frequency (by adding a capacitor or some electronics wizardry).

Changing the entire resonator makes sense but I didn't find one at the right frequency.
Hacking a 433.42 remote to send what I want makes sense as well but they're on the pricey side so I'd be happy to find a cheaper solution.

You may find this difficult because of the radio licensing in your country. Different countries restrict the garage door remote transmitters to different frequencies. The authorities actually make it difficult for the retailers to sell you the parts for another country’s frequency.

If you can buy the correct module, then do so. The amount of equipment required to change the frequency is not going to fit into the space available in an average transmitter. It will also cost many times more than a new transmitter.

Consider replacing the receiver.

The chinese who sells the product don't care much about the local regulations but in Europe, the band from 433.075 to 434.775 MHz is free.
99% of the equipment like the garage door openers and weather stations on that band use the 433.92 MHz frequency. I happen to need a 433.42 emitter.

Can I somehow hack the module to change the resonator frequency (by adding a capacitor or some electronics wizardry).

No

SAW resonators frequency pass range is defined by the geometry of the electrodes on the active
surface, they are not tunable.

Bianco:
The chinese who sells the product don't care much about the local regulations but in Europe, the band from 433.075 to 434.775 MHz is free.
99% of the equipment like the garage door openers and weather stations on that band use the 433.92 MHz frequency. I happen to need a 433.42 emitter.

You can buy the 433.42 SAW filter here. Just desolder the existing one and replace it.

Awesome, thanks!

I spend so much time on Aliexpress that I didn't check eBay. Doh!