There definitely are optics available for single mode. The problem is that the wavelength will need to match what you are being sent from your provider. So we can't really answer your question, you will have to ask them.
1310nm is quite common but we can't assume your link is 1310nm.
GPON adopts WDM to transmit data of different upstream/downstream wavelengths over the same ODN. Wavelengths range from 1290 - 1330 nm in the upstream direction and from 1480 - 1500 nm in the downstream direction.
So I guess that all the single mode SFP+ that have that range are ok.