rs232 - Ethernet Bridge

I am looking to network 3 modicon momentums M1-760-00 using RS232 to ethernet bridges, has anyone had any experience of this?

A suggestion for a suitable bridge would be welcome

would it be cheaper to swap out the existing CPUs for Ethernet models?
Another type of PLC is not an option.

I have always used the Telemecanique 174CEV bridge. It was part of the Momentum family, before they had imbeded e-net.

Lantronix DR-IAP Even has a driver for ModBus