you've got several options,
1. join the beta and get whatever is there each time.
2. google any of the following and look for what you want(HVGA is the screen type that the eris uses, NOT WVGA etc):
swype.HVGA.2.6.47.11856
swype.hvga.2.15.56.17870
Swype.hvga.2.10.52.13753
and of course there are even lower versions that still work good, many of them should work, as stated above, you remove, reboot reinstall and trial is back in play.
all swype versions are "trial" for the most part unless they've been hacked well.
good luck.