Examples of something that would work for you is
- HP/Agilent E3620A (dual 25 V, 1 A, premium quality). used only; very expensive new.
- Mastech HY3003 or HY3005 (30 V, 3 or 5 A respectively) - these come in single, dual as well as a triple which adds a 5 V supply. There are also many cloned/OEM'd versions of these. Just google images for HY-3003 and you will see. Also a.k.a. GPC-3030D and IPS-2303D (I have the latter).
You can also buy two single supplies and tie + of one to - of the other.
Consider the built-in meters. Some require you to switch between V and A, or between the two supplies. Some have inadequate resolution. The E3620A needs to switch between the two supplies but the resolution is OK (10 mV and 1 mA). The Mastech meter is inadequate for anything but rough setting (0.1 V resolution), but that's one hidden cost of a cheap supply.
I assume that you are using this to power some analog circuits like op-amps? For that I would avoid switching/SMPS supplies and go for a good old heavy linear one.