On Arrival Saudi visa for Mother through causeway

Honestly don't think you can even get a visa on arrival for your wife let alone your mother. Where did you find that information?

To come to Saudi you have to have a sponsor in Saudi. Google MOI +KSA and you should be able to find what type of visas you may get and cost of those visas.

Well I've visited Saudi Arabia with my wife through the causeway twice, her Visa was issued at the causeway as I'm a GCC citizen (Bahraini National) . No visa cost either. I was wondering if it's possible to do the same for Mom as she's under my sponsorship too.

You as a GCC citizen can enter KSA without a visa and only using your ID. However if your wife or mother is not a GCC citizen and holding different nationality but a GCC resident - they may get a visa at causeway. If mother is not a GCC resident and on visit there in Bahrain then you will have to apply a visit visa for her. You will get a transit visa as well, the visit visa will only be for Umrah unless some one else is sponsoring your mother.

So there's a chance I can take my mom direct through Causeway and get her visa issued there. Is there any link where I can get this info? I've searched many sites but no info and the Saudi embassy never picks up the call!

Unfortunately there are no sites that might give you specific or updated information. The process changes depending on person at the counter , so your best option is to check with the saudi embassy in Bahrain for more details and follow what they advise you.

I would rather take a drive and ask the immigration at causeway. Info there would be up to date and exact.