try looking for alarm ECU, in my 2000 camry solara se i4 i found it under center arm rest. on camry i think it is located behind the driver knee panel (correct me if wrong) or behind the central dash (someone else having more exp with camry may be more helpful).
it's a grey square box that says Fujitsu Ten Corp RS3000 VIP. if you find it then all you need is a remote from ebay.
programming of keyless entry fobs requires access to alarm ECU (pressing green button to activate learning mode), even used keyless fobs from ebay come with programming instructions.
just be careful as there are 2 different alarms for this model, one wa installed by factory and uses black remotes, while other (most popular) were installed by Port/Dealer and they use grey 2-button remotes.
not sure if all camry trims of that year came with keyless entry as standard.
by the way, 2000 camry is gen4. gen5 started in 2002 (non-japanese market).
this is RS3000 general user manual (including programming instructions) and installation instruction unfortunately for '98 Highlander so components location is different for camry.
http://www.4runners.org/writeups/rs3000/index.html