lpr -S filenameshould work if the software controlling the printer supports singlesided printing. The rest of this page is left for others at Rutgers who may still be using Solaris printing software.
Solaris printing software is a little different from what you're used to under SunOS 4.1.x. You queue a print request with lp and dequeue one with cancel
The command to print a file singlesided under Solaris is
lp -ynoduplex -dprinter filenameMore information about lp is available as lp_options.