Cerascreen offers an at-home antibody test. You use the kit you buy to draw a small blood sample at home and mail it to them. They use the ELISA method to test the blood for IgG antibodies and show you the result on a webpage. Not sure if this is available outside Germany, though maybe a different company offers something like this where you live.
Abbott also produces a blood test for IgG/IgM antibodies, except that it comes with a small test cassette that gives you the result directly, without sending it to a lab. Maybe importing this (or something similar) is an option for you.
There is another Covid-19 peptide vaccine developed by a Dr. Winfried Stöcker. He injected it into ≥64 volunteers, and the results he published look promising. They show both a good level of IgA, IgG and IgM antibodies and ≥ 94% neutralization for the vast majority of the test subjects. According to him (last paragraph of his blog post), none of the test subjects have reported any relevant adverse symptoms.
He describes the manufacturing in his blog (see translation below):
I’ve attempted a translation and added some of my own understanding in [square brackets]. Though I’m a German native speaker, I have zero domain knowledge in this field, so please correct me if anything is wrong:
If (!) these instructions are exhaustive, it might be easier, though possibly more expensive to produce than RaDVaC. Googling Arg319-Phe541 suggests that 100 μg (6 doses) / 1000 μg (66 doses) of this RBD can be bought for 310 € (52 € per dose) / 1130 € (18 € per dose), though there may be cheaper offers. I have no clue if the Arg319-Phe541 RBD I found here (230-01102-1000-RB listed on biocat.com and raybiotech.com) would be of the right kind to use in a vaccine.
If you have the relevant domain knowledge to evaluate how complete these instructions are or what other risks and benefits compared to RaDVaC this vaccine may have, I’d really appreciate a comment. Likewise (and especially) if you know where to buy the kind of Arg319-Phe541 RBD used for this vaccine.
If you speak German or are comfortable with DeepL: the current edition (06/21) of the German magazine “Der Spiegel” has some more background on its development on pages 44 − 46: PDF (available for free due to misprints).
Edit 1: Detailed serological results (in English) were posted by Dr. Stöcker in May 2020 when he tested the vaccine on himself first.