Do you have access to co2? You could pump a few shots of it in your fermenter before reattaching your airlock.
My wife bought one of those Soda Streams a few years back and it rarely gets used. So, I have been using it to pump a few short shots of co2 in my fermenters instead of having to top off with new must.
Adding more yeast shouldn't be necessary. There will be plenty in your mead already. Just mix honey and water til it matches the SG of your mead and use that to top it off.
As far as CO2 goes, if you don't want to buy a soda stream, you can still buy the canisters for about $15.00. Just use a pen or something to hold the tip of the canister down and there you have co2.