I like fluval cannister filters for the very reason you are finding. If something breaks or needs servicing i can easily find spare parts.
Even discontinued products lines you can still find parts fairly easily. Their website still carries parts for the 05 series which they stopped making around 2010. And a lot of their parts are interchangable between their product lines.
Im no turtle expert and couldnt recommend suitable filtration, but a 407 has similar capacity to your filter, so i would expect that to be a reasonable equivalent. Just swap the filter media from your old filter to new, squeeze out your old sponges into the water after setting up a new filter and you should preserve your cycle.
Ive had no problems with their build quality or reliabilty. When ive broken something its been my fault and its been a drive to my LFS
to pick up the replacement part and a simple fix. I regularly service my filters. As with every filter there are issues, but nothing i cant live with.
Eheim are well regarded also. Allpond solutions/ Sunsun/ Polar Aurora (they are all the same filter, branded differently in different locations) have a good reputation for their pricing. Look for something with about 9 litres capacity same as yours.