WebFaction provide a web hosting service which includes various add-ons including svn and trac.
Hosted Projects provide svn hosting starting from $7/month. They include 4 hourly off-site backup but they charge an extra fee to provide a downloadable backup.
ProSVN provide subversion hosting in Euros starting from 2 euros per month for 100Mb. I couldn't find any contact information or support info on their site beyond links to SVN clients / tutorials.
Wush provide commercial subversion hosting starting at $20/qtr or $15/month for 2Gb disk / 20Gb bandwidth including Trac. They seem to be a small company that would provide responsive support.
The Trac wiki contains a list of commercial service providers including trac hosting companies. Useful resource for trac hosting.
CVSDude provide CVS / Subversion and Trac hosting. It's free for tiny packages, a reasonable team option is $30 / month.