After some research I got these info from a Philips distributor, may they be helpful to anyone.
The M3542A paddles are not supported by philips anymore. They've been replaced by the M3543A which is water resistant.
Both are compatible with the M4735A Philips Heartstart XL defib, they have the same connector, the only thing is that regarding their size they will not fit correctly on both sides of the defibs and may be kinda loose.
The best alternatives are the M4745A sterilizable hard paddles or the M4746A with PCI, but the price is not the same.