Proc SurveySelect is not part of Base SAS, so you may not have it available to you.
Within SAS EG under Data is "Random Sample".
If coding here's an idea:
%macro select(inset,outset,size);
Data &outset;
set &inset nobs=N;
retain criteria count fudge 0;
if _n_ = 1 then criteria = N/&size;
if ranuni(-1) + fudge > criteria then do;
if count < 100 then do;
output;
count+1;
fudge+criteria;
end;
end;
drop criteria count fudge;
run;
quit;
%mend;
By increasing fudge, the probability of selecting a record increases, so that there is a greater change of selecting a particular record.
The downside to this method is that the actual probability distribution is not uniform. If fudge were not used, and "uniformity" maintained, then in a single pass through the dataset, you might not get all "size = 100" records/observations.
An alternative would be to use the POINT= set option
data &outset;
retain count 0;
I = ranuni(-1) * N;
set &inset NOBS=N POINT=I;
count+1;
if count = &size then stop;
drop count;
run;
quit;
This is probably a better method, and can also be encased in the above macro.