Looking for suggestions on where to get inexpensive parts to use for wiring connections. Used to be we could rely on Radio Shack but that's no longer an option. Say I need to tap into my turn signal wiring to attach some sequential side marker lights. I don't feel compelled to buy what's offered at any of the local auto parts stores. What they want for as little that they offer doesn't sound appealing. Thanks in advance for any info.

Heat-shrink crimps and solder-shrink butt connectors are God's gift to good wire repair. Stuff like this is available all over eBay and Amazon:
https://www.ebay.com/itm/195404051909
https://www.ebay.com/itm/224785730481