Tank H2 could work for you.  It depends how it is prepared by the 
supplier.  We have found that it tends to be highly depleted (-700 
per mil).  We have been using a tank of prepared H2 from a company 
called "OzTech Trading Corp." which supplies a gas that is close to 
the middle of the range that we normally operate (-250 to +20 per 
mil).  We got it through ISO-MASS Scientific of Calgary, Alberta, 
Canada.  We have been using it for about two years now.

As Dr Coplen suggested in the previous reply:
"One should not necessarily expect that the delta value of the working
standard of such tank gas will remain constant.  It is best to prepare
secondary reference materials for use in your laboratory and to calibrate
them using VSMOW and SLAP.  Then analyze these secondary reference materials
daily, weekly, or as needed in order to calibrate your hydrogen
isotope-ratio scale."

   The internal reference materials can be prepared in different 
ways.  For example we use three standards that fall in the range of 
analysis that is typical of natural abundances.

STD      Delta D (Smow)
-1=      -227.62 per mil (From arctic ice)
-2=        -84.06 per mil (Local distilled water)
-3=       +15.63 per mil (Dillution (heavy water+Local water))

    The dillution is fairly simple using M1V1=M2V2=M3V3
Where M1= Final concentration
            V1=  The final volume you want
            M2= concentation of local water
            V2=  dillution volume of heavy water
            M3= concentration of heavy water
            V3=  volume of heavy water
M= concentration in per mil.
V= volume in (say) ml.
Ex:  Local water= 80 per mil
       Heavy water= 2000 per mil
       Final dilution = 15 per mil
For 2000 ml at 15 per mil you would add 15ml of heavy water to 
1985ml of local water.
When I prepared my standard I came to 0.6 per mil of my target using 
this technique.
After you have your internal standards you simply calibrate them 
using SLAP & SMOW and run a check using GISP, or use the help of 
another lab.
Gilles St-Jean, U. d'Ottawa / Geologie
140 Louis Pasteur, Ottawa, Ontario, Canada, K1N 6N5
Tel: 613 562-5800 ext: 6839(Bureau / Office)
     613 562-5800 ext: 6836(Lab)
Fax: 613 562-5192