Replacement aluminum electrolytics capacitors (CDE or Mallory) are readily available. CDE has a web site catalog for a wide range of capacitors. Notice that CDE also prominently posts the Load Life (in hours) of various capacitor models.
Mouser is a CDE/Mallory distributor - and should be able to get any capacitor you see on the CDE web site. CDE discontinued direct Internet sales earlier this year.
CDE Aluminum Electrolytic Capacitors
For your SB-200, I recommend that you look at the PW-202 board from Harbach Electronics.
The PW-202 is a complete replacement for the old SB-200 power supply board. It features matched computer grade filter capacitors, modern 1000 volt diode rectifiers and a precision high voltage meter resistor string. Included with the PW-202 is the Harbach soft-start module, which reduces the turn-on inrush current to a mere 6 amperes.http://www.harbachelectronics.com/reference/harpg2cart.htm
Jeff Weinberg - W8CQ
468 County Road 620, Polk, OH 44866
Telephone & Fax (419) 945-2359
Harbach also has a SoftKey module SK-201, to reduce the SB-200 keying voltage for usage with modern solid state transceivers. Jeff has the SK-201 installation instructions available here:http://www.harbachelectronics.com/pdffiles/sk-201.pdf
While you have the SB-200 on the workbench, take time to read and review photographs from
SB-200 Amplifier Rebuild Notes by Bob Norgard, KL7FMhttp://home.gci.net/~rnorgard/ampnotes.html
Bob did have a kit of parts available at one point, but many of the parts mentioned in his notes are readily available from: Mouser; DigiKey; and RF Parts