I'm no expert but would try this,

Buy cheap android phone £50 and Install Electrum from Google play or better from Electrum.org using their method to verify the download is genuine.

From this point make sure the phone NEVER has internet until funds moved to your new hardware wallet address.

Using Anroid phone import a 2of2 multisig into Electrum with option "I already have seeds".  Use Bip39 when importing the hardware wallet seed.  The share addresses should match those on Mac when setup complete.

Now create the online transaction with your Mac computer and export the QR code so the phone can scan and sign the transaction.

Export the signed QR code from phone back to the Mac computer using scan option and transmit the transaction from your Mac computer to your new hardware wallet address.

Obviously the two sets of the seeds you used to recreate the multisig on the the phone  would have to be 2 of the 3 used when you created the Mac multisig.