Adding Keyless entry to an 850

Hi.

I have a 1994 850 that I thought might have keyless entry, but it doesn't. I have the level I which doesn't have the keyless entry as a standard feature.

Is there a Volvo part to add this feature on? I believe that it was a dealer added option on my model car and I will do it myself. I would prefer to use OEM parts rather than an after-market.

Can anyone shed some light here?

Thanks!