Here's what I found. The stock C50 (I have an 05 model, so this info is only relevant for 05-08 C50 or M50 bikes) injectors are made by Keihin (you can see their "K" logo stamped on them) and are their code C. On Keihin injectors, the single letter code refers to flow rate. The other codes underneath the electrical connector refer to batch/date of production and ultimately meaningless.
Punch "Keihin C injector" into google and a-ha, it turns up a plethora of fitment for Civics throughout most of the '00s. Honda part # 16450-PLC-003, but also commonly referred to simply as a Keihin "C stamp" or "type C". Physically they appear identical. They are also 4 hole injectors. That Honda part has a plethora of cross references as well.
GB Reman 842-12282
Ebay is littered with those (or rockauto, or virtually anywhere). Prices are generally around $20-25 apiece for either new aftermarket or remanufactured Keihin's. Far cry better than $220 for one from Suzuki.
But, what about actual flow rate- just because they look the same doesn't mean they are. This was tricky, as far as I can tell there are no readily available or published specs for these in OEM fitments. All data is from independent testing by performance shops or injector remanufacturers that have cleaning/flow test rigs.
Shows a test of stock C50 injectors. The post-cleaning result shows approximately ~57cc's of flow after a 30 second test at 50% duty cycle. That equates to about ~224cc/min flow rate (standard measurement).
Looking up stock injector size for a Honda D17A6 engine, tests all point they are anywhere between 220 and 230cc/min, again, depending on who did the test. Some variance is to be expected, but the agreement is right in that range. 3 bar (44psi) also seems to be largely standard for port fuel injecton systems, so this should be apples to apples.