...and I can't find new ones because peer discovery is done through UDP and tor only runs through TCP. Is this an accurate understanding?
Yes.
As per the issue thread you linked to, you could attempt to add peers (using --reserved-peers) from the hard-coded bootnodes list in the ETC codebase, located in bootnodes.go.
The list, as of late January 2017, is as follows: e by supplying a default list, parsing oracle & random selection
discover.MustParseNode("enode://08c7ee6a4f861ff0664a49532bcc86de1363acd608999d1b76609bb9bc278649906f069057630fd9493924a368b5d1dc9b8f8bf13ac26df72512f6d1fabd8c95@45.32.7.81:30303"), //dan-
discover.MustParseNode("enode://e809c4a2fec7daed400e5e28564e23693b23b2cc5a019b612505631bbe7b9ccf709c1796d2a3d29ef2b045f210caf51e3c4f5b6d3587d43ad5d6397526fa6179@174.112.32.157:30303"), //bar-
discover.MustParseNode("enode://687be94c3a7beaa3d2fde82fa5046cdeb3e8198354e05b29d6e0d4e276713e3707ac10f784a7904938b06b46c764875c241b0337dd853385a4d8bfcbf8190647@95.183.51.229:30303"), //tre-
discover.MustParseNode("enode://6e538e7c1280f0a31ff08b382db5302480f775480b8e68f8febca0ceff81e4b19153c6f8bf60313b93bef2cc34d34e1df41317de0ce613a201d1660a788a03e2@52.206.67.235:30303"), //ela-
discover.MustParseNode("enode://ca5ae4eca09ba6787e29cf6d86f7634d07aae6b9e6317a59aff675851c0bf445068173208cf8ef7f5cd783d8e29b85b2fa3fa358124cf0546823149724f9bde1@138.68.1.16:30303"), //ige-
discover.MustParseNode("enode://217ebe27e89bf4fec8ce06509323ff095b1014378deb75ab2e5f6759a4e8750a3bd8254b8c6833136e4d5e58230d65ee8ab34a5db5abf0640408c4288af3c8a7@188.138.1.237:30303"), //lec-
discover.MustParseNode("enode://fa20444ef991596ce99b81652ac4e61de1eddc4ff21d3cd42762abd7ed47e7cf044d3c9ccddaf6035d39725e4eb372806787829ccb9a08ec7cb71883cb8c3abd@50.149.116.182:30303"), //Vla-
discover.MustParseNode("enode://4bd6a4df3612c718333eb5ea7f817923a8cdf1bed89cee70d1710b45a0b6b77b2819846440555e451a9b602ad2efa2d2facd4620650249d8468008946887820a@71.178.232.20:30304"), //NoM-
discover.MustParseNode("enode://921cf8e4c345fe8db913c53964f9cadc667644e7f20195a0b7d877bd689a5934e146ff2c2259f1bae6817b6585153a007ceb67d260b720fa3e6fc4350df25c7f@51.255.49.170:30303"), //jai-
discover.MustParseNode("enode://ffea3b01c000cdd89e1e9229fea3e80e95b646f9b2aa55071fc865e2f19543c9b06045cc2e69453e6b78100a119e66be1b5ad50b36f2ffd27293caa28efdd1b2@128.199.93.177:3030"), //pys-
discover.MustParseNode("enode://ee3da491ce6a155eb132708eb0e8d04b0637926ec0ae1b79e63fc97cb9fc3818f49250a0ae0d7f79ed62b66ec677f408c4e01741504dc7a051e274f1e803d454@91.121.65.179:40404"), //mso-
discover.MustParseNode("enode://48e063a6cf5f335b1ef2ed98126bf522cf254396f850c7d442fe2edbbc23398787e14cd4de7968a00175a82762de9cbe9e1407d8ccbcaeca5004d65f8398d759@159.203.255.59:30303"), //mik-
discover.MustParseNode("enode://42d8f29d1db5f4b2947cd5c3d76c6d0d3697e6b9b3430c3d41e46b4bb77655433aeedc25d4b4ea9d8214b6a43008ba67199374a9b53633301bca0cd20c6928ab@104.155.176.151:30303"), //boot.gastracker.io