too late for OP. May be useful for others.
I am in Suzhou on an L tourist visa. I successfully (I hope) applied yesterday in Suzhou PSB for a 30 day "extension".
Details:
When: Operating hours are from 9am-12pm, 1pm-5pm, Monday-Friday
Where: Division of Entry-Exit Administration of the Suzhou Municipal Public Security Bureau, Suzhou Administrative Service Center, 389 Sanxiang Road.
What to bring:
1. Your passport
2. your Registration Form of Temporary Residence got from the local police station (where you were staying), Public Security Bureau (PSB), or from your current hotel (and a photocopy)
3. one passport-size (2x2 square-inch) white background photo.
4. Your flight "itinerary" of your intended flight out of China (as proof that you will leave in the next 30 days). (i.e. a print of your flight confirmation).
5. Application form (which) is provided for completion while you are at the Entry/Exit Bureau. Simple form in English.
6. They also require photocopy of passport photo page, most recent entry stamp page, current visa page.
7. As well as the application form, they have a second form that requests details of your intended tourist itinerary for the extension period.
You do NOT need proof of 20,000 RMB in an account. Apparently this IS runoured to be the case in Beijing but I don't know for sure if that is true in practice.
How much: 160 RMB
There is a photocopy counter just inside the main door in the first part of the room.
Some more details of the process as far as I can remember:
After you fill in the application form, take your documents to the counter on the top left of the main room (the first two un-numbered desks). The staff can check your documents and tell you if anything is missing or incorrect.
Then go slightly back to the "middle" of the large room to get a number. Your number will not be in sequence with the rest of the Chinese who are registering change of City. But don't panic, it will miraculously appear quite soon on the large screen at the top of the room in the middle of the sequenced other numbers.
After your number comes up, go to the relevant desk and they will check some details in their system. If all is ok, they will give you a printed summary paper of your application to go and pay the fee in the first part of the room (opposite the main door).
You pay and bring back a payment receipt back to the same desk.
They send you up to desk 19 who will do something with your paper and receipt.
Then you go back to the original desk and they take one piece and give you back your receipt for the collection.
A week later you go back to desk 19 and collect. (Don't think you require a number. Just barge in talking over anyone in front of you. Its China after all.).
I found them to be quite amenable to the extension so long as I provided my printed intended exit flight details.
And they were quite mannerly and easy to deal with.
It is actually a very efficient (albeit chaotic looking) operation.
I applied 4 days in advance of the last day of my L visa.
If you intend to arrive on the last day of your visa eligibility, I would suggest you bring along a Chinese friend who is very good at apologising on your behalf.
Alternatively, and preferably, do it a number of days beforehand.
