i just made my own uniseals by casting two originals in silcone rubber , then using a marrine rubber to make the seals with polyurethane composite el110h/bk or el230r/bk .
i did this as uniseals are so expensive these come in at about £3 each
they work well i used these ones on septic tank in the end , no leaks etc , i used a silicone mold making kit and casted off my original uniseals as shown in the pics , the material i used is for extreme environments so it does not degrade at all in water , or chemicals .