1966 Valiant Signet Park/Signal lamp problem

On the risk of sounding stupid, here goes: my friend said she has no right turn signal. I found the front bulb not to be working. The problem is, I can not get another bulb to go into the socket, turn & lock into place. I now have the parklamp housing off the car, & clamped in my vise-still nothing. I have tried several 1157 bulbs, to no avail. At this point, I feel that the socket must be bad. Judging by the connector, I believe the socket is correct for the car, not something that someone mickey moused. OK, so I'll replace the socket-not so easy. All the replacement listings I see on line are for a single lead socket, clearly not correct for this car. Where can I get the correct front park signal lamp socket, or even the entire housing & socket assembly for this car? Thanks.