I've owned the Soliloquy 5.0's and still have a pair of the Sat5's. When I bought the Sat5's one had a bad tweeter so I had to try to track down a replacement.
I'm not sure about the 5.3's but I think all the Soliloquy drivers were proprietary Phil Jones designs. I found a pair of tweeters at Underwood HiFi because Walter had bought some of the remaining stock when Soliloquy shut down. I think I got the last two of the tweeters that were used in the 5.0 and Sat5 but it would be worth giving him a call. I couldn't find any other source at the time I was looking.
I'm not sure about the 5.3's but I think all the Soliloquy drivers were proprietary Phil Jones designs. I found a pair of tweeters at Underwood HiFi because Walter had bought some of the remaining stock when Soliloquy shut down. I think I got the last two of the tweeters that were used in the 5.0 and Sat5 but it would be worth giving him a call. I couldn't find any other source at the time I was looking.