There still are resellers of rotational smaller capacity HDDs online, if not in computer repair shops nearer your community.
Larger conglomerate sellers or collectives of online shops such as amazon offer a variety of replacement options; but to
put too much into an older computer may be questionable.
But what is too much? My original build MacBook1.1 13-inch 1.83GHz initial offered as first model in 2006 still goes OK
with an 'upgrade' from slower rotational shipped 5400-RPM hard drive, to 7200-RPM with modest increase to 180 GB
and that runs the highest last version of Mac OS X it can support. But have settled on Leopard 10.5.8 instead of 10.6.x.
A good web browser exists for these older mac OS X in a custom build version based on mozilla, by TenFourFox. I use it
in the earlier Intel-based mac because those include a utility that allows older PPC-based software to run w/ Intel CPU.
Upgrade to Lion 10.7 removes that happy probability. So If you need more software than can be utilized in older Macs
then consider what that may be, and define its mission. Also check into availability of new battery replacement, etc.
A few good models of SSD can be used in older Mac and PC portables, from different vendors; owc macsales has some
that do well and are tested in older & newer hardware series mac. And the early MacBooks are easier to upgrade their HDD
(to higher capacity rotational, or also to SSD/solid state) than older PowerBook/iBook G4 models.
So the matter of cost could be similar if best suited capacity (lower cost, smaller capacity) may be considered; and also
consider an external enclosure to still make use of the SSD or larger HDD/rotational as storage. The SSD design for the
older MacBook should be realized to be over-spec; but backward compatibility is suggested.
The system bus and processor speeds (data transfer rate) for newer drive replacement should consider that backward
compatibility is within specification when stated by drive makers. I'd get an SSD of lower speed than most recent build
-or- locate a cost efficient higher rotational HDD. ~ Figure the mac may not last 5 years before other worn parts fail.
And you may tire of chasing parts that may cease to be available as time goes on... But you could still be using it.
Two rotational (including one hybrid) drive replacements exist among other modern SSDs offered at owc macsales
at cost efficiency worth consideration.
internal drive options for macbook (1.83/2.0GHz 13-in)
https://eshop.macsales.com/upgrades/macbook-13-inch-mid-2006-1.83-ghz/internal-drives
slower better 'compatible' data transfer speed example, first:
500GB Mercury Electra 3G 2.5-inch 7mm SATA 3.0Gb/s Solid-State Drive
backward compatibles exist from owc & other makers, check specs
1.0TB HGST Travelstar 7K1000 2.5-inch 9.5mm SATA 6.0Gb/s 7200RPM Hard Drive (under $70)
..and other rotational + solid state drives, enclosures; also [ Install Videos ] instructions on site..