Can anyone reccomend an affordable way to sign my macros?

Self-cert is no good for me as the tick-box to "always trust content
from..." is only available on the machine it was created on.

But I can only find certificates that cost hundreds of dollars a year.

I'm happy to pay for a certificate, but they seem VERY expensive for what
I'm going to use them for. AND they only last for a year.

Have I missed something? Is there a longer lasting one, or a cheaper
alternative? Or can I do something to enable the "Always trust content
from..." tick box so that I could use the self-cert option?

All input vey gratefully received

Thanks

M