Flush/slotted actuated rotary switch knob?
The rotary switch under discussion is typically used for preset / factory setting or maintenance purposes - such as for setting a part of a device address, a configuration value to be read during device operation, or selection of power path for enabling one of several circuit sub-sections. 

The particular part you have selected has silver-plated copper contacts (Q suffix) for power routing, rather than low-level signal routing or configuration setting.

The lack of available knobs for this type of switch aligns with the design goal of not making it convenient for end-users to make changes - like having a sticker "No user-serviceable parts inside".

For a hand-actuated equivalent, look for flatted actuator, or knob actuator designs. Some thumbwheel actuated designs are also very cost-effective, especially on eBay or other such sites. 



A quick search indicates you may be able to find thumbwheels cheaper than the device you have selected, if 10 positions are not a firm requirement.

Another reason for going with thumbwheels is that they are less obtrusive than knob / shaft devices, hence allowing sleeker enclosures!