Whatever you do, test it out on a scrap piece of t-shirt material first! I don't know about the oil-based Sharpie, but I do know that permanent Sharpie pens (black ones) tend to bleed when used on fabric. I do think you may have difficulties finding a pen that will cover up black. My suggestion would be Shiva Paint Sticks. I haven't used them myself, but I know quilters use them on quilts. They are probably available in art stores such as Dick Blick's and Michael's, and also on Amazon. Here is a link to a Youtube video about them:
https://www.youtube.com/watch?v=m2WbRdAuuKQ
There are many different colors, some irridescent. You might want to look for a silver or gold, but here is a link to a white one on Amazon:
https://www.amazon.com/Jack-Richeson...dp/B000A8B1HS/
If you Google, you may be able to find someone who has used them on t-shirts. I'm not sure you can get a fine line with these, but I'm thinking an outline in irridescent silver could achieve what you are looking for.
Edit: You could probably achieve a thin line by creating a raised template to place underneath the t-shirt front, so you would be "rubbing" the outline onto the shirt. Not sure how you would create the template, but it should be possible.
Do note that you need to let the paint dry for 3 to 5 days before ironing to make it washfast. This is not something you want to postpone until the day before Christmas!
Edit 2: I did a search of the reviews on Amazon for the Sharpie oil-based paint marker. I will link my search on the word "fabric" but, in case it doesn't work, it appears to me from a cursory reading that it works best on hard surfaces. This is because the tip of the marker needs to be depressed in order to soak up the paint. If you do try it on t-shirt fabric, you would need to have a hard surface underneath it. Several of the reviews say it doesn't work well on fabric, that it is too faint to cover up other colors and that it is either soaked up by the fabric or bleeds into the fabric. Here is the link:
https://www.amazon.com/Sharpie-Oil-B...ews-filter-bar